Fungicidal coating compositions containing quaternary ammonium salts as the active ingredient in either polymeric emulsions or directly bonded to polymers are known. See U.S. Pat. Nos. 4,866,106, 4,990,547, 5,084,096 and 5,096,488. However, such compositions have fairly high quaternary ammonium content, are susceptible to chemical breakdown by exposure to UV light, do not adhere well to vertical surfaces, and tend to leach out the active ingredient rather rapidly due to the exposure to salt water and rain and washing. There is therefore a need in the art for a fungicidal composition that has a lower quaternary ammonium content, that is chemically stable, that adheres well to vertical surfaces, and that is resistant to active ingredient washout. These needs are met by the present invention, which is summarized and described in detail below.